Lacrimal gland acinar cells secrete an important array of bacterial tear proteins which are critical for the health of the ocular surface. The goal of this proposal is to characterize the role of a heretofore unexamined group of novel lower molecular weight basement membrane molecules in modulating tear protein secretion during lacrimal gland development and disease. The exorbital lacrimal gland, located adjacent to the eye in its superior lateral aspect, contains a vast number of basement membranes which appear in cross-section as linear peri-acinar structures. When freshly isolated lacrimal acinar cells are plated on an EDTA extract of basement membrane, tear protein secretion becomes augmented after only 24 hr in culture. This phenomenon appears to be attributable to a group of one or several uncharacterized lower molecular weight molecules, possibly including three apparently novel lacrimal acinar cell attachment peptides of 25, 40 and 65 kD to which monoclonal antibodies have been prepared. The specific aims of this proposal are: (i) to identify and partially characterize basement membrane peptide(s) responsible for augmenting tear protein secretion, (ii) to immunopurify, obtain N-terminal sequence, and initiate cDNA cloning of the low molecular weight attachment peptides, and (iii) to use immunoperoxidase, immunoprecipitation, and in situ hybridization to characterize the histological, developmental and disease distribution of peptides identified in aims (i) and (ii). The approach is to use a systematic molecular screening strategy combined with a sensitive peroxidase secretion assay and unique monoclonal antibodies to identify active molecule(s) in the EDTA basement membrane extract. These studies may open the door to a new molecular understanding of dry eye in ageing and disease.